Hologic, Inc. v. Minerva Surgical, Inc.

A named inventor assigned his patent applications to a company he had co-founded in order to commercialize the technology disclosed in the applications. The company was acquired by Hologic, and the named inventor/co-founder left to start a directly competing company, Minerva Surgical. Hologic sued Minerva for infringing patents that issued from the assigned patent applications, and Minerva sought to invalidate the patents. The Federal Circuit held that, under Federal Circuit precedent, "assignor estoppel'' barred Minerva from challenging the validity of the patents in district court proceedings. However, the court held that Minerva was not barred by assignor estoppel from challenging the patents through inter partes review (IPR) proceedings, again based on binding Federal Circuit precedent. Minerva succeeded in invalidating one of the patents through IPR, and that decision was affirmed by the Federal Circuit. The court held that the patent assignee (Hologic) was collaterally estopped from asserting the patent "in any further proceedings'' in view of its affirmance of the Board's invalidity decision. Writing separately, Judge Stoll suggested "that it is time for this court to consider en banc the doctrine of assignor estoppel as it applies both in district court and in the Patent Office. We should seek to clarify this odd and seemingly illogical regime in which an assignor cannot present any invalidity defenses in district court but can present a limited set of invalidity grounds in an IPR proceeding.''